Cyclopropenoid fatty acids (CPFA) which occur in certain foodstuffs such as "Cot-N-Nuts," cottonseed oil and flour; kapok oil and okra are known to have toxic effects when consumed by animals. These unique compounds are known to impair reproduction in rats and chickens, alter the fatty acid composition in the body lipids of several species, and cause characteristic alterations in trout and rabbit liver parenchymal cells. In addition, our studies have demonstrated that CPFA act as powerful cocarcinogens with aflatoxin B1 and as carcinogens in the induction of liver cancer in rainbow trout. This research shall have as the primary goals an explanation for the cocarcinogenic and carcinogenic activity of CPFA, and the expansion of our knowledge of their toxic effects in trout and other animals. To attain this goal the effect of CPFA on the microsomal mixed function oxidase system and on the activation and detoxication of aflatoxin B1 will be determined and correlated with induction of tumors. The effect of CPFA on microsomal membrane lipid composition and structure will be investigated to determine if CPFA have an indirect effect on enzyme activity by influencing the membrane lipid environment of the enzyme. The structural specificity required for cyclopropene activity will be investigated by measuring biological activity of malvalate, the predominant CPFA in foodstuffs, and hydrocarbon homologous analogs of CPFA.